package Circonferencia;
import java.util.Scanner;
import java.util.Locale;

public class Circulo {

	public static void main(String[] args) {
		Locale.setDefault(Locale.US);
		Scanner sc = new Scanner(System.in);
	    double r = sc.nextDouble(); double pi = 3.14159; double R = r * r; double area = pi * R;
	    
	    System.out.printf("A=%.4f\n", +area);
	    
	    sc.close();

	}

}
